1. Field of the Invention
The present invention relates to an optical waveguide having a clad made of a fluorinated alicyclic structure-containing polymer having functional groups, which has a high adhesion to the substrate, and which has low transmission loss.
2. Description of the Background
It has been known that by using an amorphous fluorine-containing polymer as a material for an optical waveguide, the transmission loss can be made small, the rate of the moisture absorption can be made low, and the light scattering resulting from birefringence can be suppressed (JP-A-4-190202).
However, if the amorphous fluorine-containing polymer is used for the clad of an optical waveguide, the adhesion to the substrate tends to be low. Accordingly, in the case where layers of clad and core are successively formed on a silicon substrate, and the core is processed to have a desired shape to prepare an optical waveguide, for example, the clad made of the amorphous fluorine-containing polymer is likely to peel off from the substrate or the core. Further, in the case where the optical waveguide part is cut out from the substrate after the optical waveguide is formed, the clad is likely to peel off from the substrate. Still further, in the case where the amorphous fluorine-containing polymer is used for the core of the optical waveguide, as the refractive index of the material itself is low, a material having a lower refractive index required for the clad of the optical waveguide is hardly available.